The SPC is forecasting ...Severe thunderstorms expected over parts of the Midwest into the lower Great Lakes this afternoon and tonight....
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the latest public statement about this event. View What is a Watch? clip.

Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.

SPC AC 301952
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0252 PM CDT MON JUN 30 2014
VALID 302000Z - 011200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MIDWEST
FROM ERN IA INTO SWRN LOWER MI/NWRN INDIANA...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
LOWER MI...SWWD INTO THE TX PANHANDLE...
...SUMMARY...
DAMAGING SQUALL LINE WITH WIND GUSTS POSSIBLY EXCEEDING 60-70 MPH
WILL SPREAD ACROSS EASTERN IOWA AND NORTHERN ILLINOIS/SOUTHERN
WISCONSIN BY 7PM. SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED
ACROSS THE SURROUNDING MIDWEST INTO THE CENTRAL AND SOUTHERN HIGH
PLAINS OF THE TEXAS PANHANDLE.
...EASTERN IA/NORTHERN IL/SOUTHERN WI...
CLUSTERS OF CONVECTION THAT ORIGINATED OVER THE MID MO VALLEY HAVE
RECENTLY EVOLVED INTO A MATURE SQUALL LINE OVER EASTERN IA. WHILE
MULTIPLE STORM MODES WERE NOTED EARLIER IN THE CONVECTIVE
EVOLUTION...IT APPEARS A WELL-ORGANIZED DAMAGING MCS WILL RACE
ACROSS ERN IA INTO NRN IL/SRN WI OVER THE NEXT 4-5 HOURS. LEADING
EDGE OF THIS ACTIVITY IS SURGING EAST AT 50KT+ AND NUMEROUS MEASURED
WIND GUSTS OF 50-64KT HAVE BEEN REPORTED IN THE LAST HOUR OR SO
ACROSS IA. IF SQUALL LINE CONTINUES TO ACCELERATE WIND SPEEDS COULD
EASILY EXCEED 65KT AT THE APEX OF THIS EVOLVING BOW AS IT SPREADS
INTO NRN IL. GIVEN THE CURRENT SPEED/MOVEMENT IT SHOULD SPREAD INTO
WESTERN PORTIONS OF METRO CHICAGO BETWEEN 5-6 PM. DAMAGING WINDS
ARE HIGHLY LIKELY WITH THIS CONVECTION.
ELSEWHERE...EARLIER THOUGHTS REGARDING CONVECTIVE POTENTIAL REMAIN.
..DARROW.. 06/30/2014
.PREV DISCUSSION... /ISSUED 1133 AM CDT MON JUN 30 2014/
...SYNOPTIC SETUP...
SEASONABLY STRONG...CYCLONIC MID/UPR-LVL FLOW WILL PREVAIL OVER THE
N CNTRL STATES THROUGH TUE...ON SRN SIDE OF SLOWLY-PROGRESSIVE
MB/ONT UPR LOW. A FAIRLY SUBSTANTIAL SHORTWAVE IMPULSE IN THIS
FLOW...NOW OVER THE NRN HIGH PLNS...WILL SWEEP E INTO THE UPR MS VLY
BY THIS EVE...BEFORE TURNING NE ACROSS THE UPR GRT LKS EARLY TUE.
AHEAD OF THIS TROUGH...EXPECT LOW-AMPLITUDE DISTURBANCE NOW OVER
CNTRL NEB TO TRACK RAPIDLY ENE INTO LWR MI EARLY TUE.
AT THE SFC...COLD FRONT ASSOCIATED WITH MB/ONT LOW WILL PROGRESS
STEADILY E ACROSS THE UPR MS VLY...AND SE ACROSS THE CNTRL PLNS.
AHEAD OF THE FRONT...A SERIES OF LOOSELY-CONNECTED OUTFLOW
BOUNDARIES EXTENDING ROUGHLY WNW-ESE FROM ERN NEB TO CNTRL IL/IND
LIKELY WILL PERSIST THROUGH TNGT. THE BOUNDARIES MAY DRIFT A BIT
NEWD ACROSS ERN IA AND IL TODAY...BUT NEWD ADVANCE MAY BE OFFSET IN
PLACES BY POTENTIAL STORM DEVELOPMENT IN THE REGION THIS AFTN.
FARTHER SW...LEE TROUGH/DRY LINE WILL PERSIST OVER THE SRN HIGH
PLNS.
...CNTRL PLNS TO MID/UPR MS VLY AND LWR MI TODAY/TNGT...
SETUP APPEARS FAVORABLE FOR SIGNIFICANT SVR WEATHER OVER THE LWR MO
AND MID MS VLYS TODAY INTO TNGT. A BAND OF MODERATE TO STRONG WLY
DEEP SHEAR WILL OVERLIE A SIMILARLY-ORIENTED CORRIDOR OF SUBSTANTIAL
INSTABILITY IN THE PRESENCE OF AT LEAST MODEST LARGE-SCALE FORCING
FOR ASCENT. THIS SETUP COULD YIELD FAIRLY NUMEROUS SUPERCELLS THAT
WILL HAVE THE POTENTIAL FOR UPSCALE GROWTH INTO A DERECHO-PRODUCING
MCS.
TSTMS NOW OVER ERN NEB AND WRN IA /REF WWS 372 AND 373/ ARE FORMING
IN ZONE OF STRONGEST WAA/MOISTURE TRANSPORT AHEAD OF NEB/KS UPR
IMPULSE. THIS ACTIVITY SHOULD INCREASE IN COVERAGE/STRENGTH AND
MOVE/DEVELOP GENERALLY ESE TOWARD THE MS RVR TODAY AS SFC HEATING
FURTHER DESTABILIZES AREA ALONG AND N OF DIFFUSE OUTFLOW BOUNDARIES
/SBCAPE INCREASING TO AROUND 4000 J PER KG/. AREA VWP DATA SHOW DEEP
WIND PROFILES BACKING ATTM...BUT REMAINING STRONG...AHEAD OF THE
NEB/KS DISTURBANCE. PROFILES SHOULD REMAIN FAVORABLE FOR SUPERCELLS
AND OTHER SUSTAINED STRUCTURES THROUGH THE AFTN. THESE WILL BE
CAPABLE OF VERY LARGE HAIL...HIGH WIND...AND TORNADOES. DEPTH OF
STRONG...LARGELY UNIDIRECTIONAL CLOUD-LAYER FLOW AND DEGREE OF
LOW-LVL BUOYANCY ALSO SUGGEST THAT SETUP WILL REMAIN FAVORABLE FOR
BOW-ECHOES AND MORE CONTINUOUS SWATHS OF DMGG WIND. THIS ACTIVITY
MAY FURTHER AMALGAMATE INTO A DERECHO-PRODUCING MCS THAT CONTINUES
E/ESE INTO IL BY EVE.
FARTHER DOWNSTREAM FROM THESE STORMS...BUOYANCY WILL REMAIN SOMEWHAT
MORE LIMITED THIS AFTN E/SEWD INTO THE LWR OH VLY.
NEVERTHELESS...SOME POTENTIAL WILL EXIST FOR DIURNAL STORM
DEVELOPMENT OVER IL/IND THROUGH THE AFTN IN RESPONSE TO SFC HEATING
AND STRENGTHENING/MOIST SW LOW LVL FLOW AHEAD OF NEB/KS IMPULSE.
THESE STORMS COULD PRODUCE LOCALLY DMGG WIND/SVR HAIL.
...S CNTRL PLNS THIS AFTN/TNGT...
STRONG HEATING OF MOIST...VERY UNSTABLE /SBCAPE AOA 4000 J PER KG/
AIR AHEAD OF COLD FRONT AND SWD ALONG LEE TROUGH/DRY LINE WILL
LIKELY RESULT IN RAPID DEVELOPMENT OF INTENSE STORMS SWWD ALONG
THESE BOUNDARIES BY MID TO LATE AFTN AS EML CAP IS BREACHED BY
LOW-LVL UPLIFT. AMPLE /40+ KT/ WSWLY DEEP SHEAR WILL EXIST IN KS FOR
SUPERCELLS WITH LARGE HAIL/SVR WIND AND TORNADOES. DEVELOPMENT ALSO
WILL BE FOSTERED BY ASCENT WITH NEB/KS UPR IMPULSE. FARTHER
S...SOMEWHAT WEAKER SHEAR AMIDST VERY STRONG INSTABILITY SUGGESTS A
MORE MULTICELLULAR/TRANSIENT SUPERCELL MODES WITH SWD EXTENT...BUT
WITH A CONTINUED THREAT FOR SVR HAIL/WIND/ISOLD TORNADOES. THESE
STORMS MAY EVOLVE INTO ONE OR TWO SE-MOVING CLUSTERS WITH EMBEDDED
BOWING STRUCTURES BY LATE EVE.
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